In the commercial digital printing business, the need for regularly calibrating the color printers employed is both known and accepted--not only when the ink supplies are replenished, or when different papers or canvases are to be printed on, but over various intervals of time as well, as the hole sizes of the ink cartridges wear with time getting larger through continuing use. Because the characteristics of the inks may change, or the light reflective characteristics of the papers or canvases may be different, or the amounts of color inks put down increase, the end result has been appreciated to be a color print different from those previously made on that printer, even where the computer generated signal continues to be exactly representative of the image originally scanned. For such reasons, it is not unusual to find the color printer manufacturer supplying along with such equipment a calibrating device in the form of a densitometer for color management. The intention of such cooperation is to analyze the colors reproduced, and to calibrate the printer if need be, usually at its Raster Image Processing Software of the on-board computer included in its construction.
A typical procedure in so calibrating the printer revolves around the standards as to how much of each of Cyan (C), Magenta (M), Yellow (Y) and Black (K) reference colors are in a printed strip. Thus, in this widely accepted procedure, the four colors CMYK are printed out typically in groups of five different shades for each color (or as few as one shade per color), and with the calibrator then reading each shade, for storage in the Raster Image Processing Software. With the calibrator also being employed to take a reading of the paper or canvas (termed the "White Point"), everything is stored and then later compared when the paper or canvas is changed, when the inks are changed, and over time because of printer drift.
While such arrangements have been accepted by those operating in the digital printing business with a single computer feeding a single printer, such arrangement has been determined to provide generally unsatisfactory results when that single computer feeds color corrected images to several printers over a network, as is the situation with a more elaborate digital printing business. More specifically, the printed images were observed to have various degrees of "tinting" when compared from one printer output to another. Whereas such differences might not be wholly objectionable to an owner of a print as to whether the sky was "bluer" than it should be, or that trees were "greener" than in the actual scene, the "tinting" becomes more objectionable if a pictured snow fall in that print turned out to have a "pinkish" or "yellowish" tinge. Where a typical run of one or more prints are to be made from a photograph, for example, these different tinges of "pink" or "yellow" not only would become objectionable, but would become more so from copies produced from one printer, as compared to another.
Review and analysis of the situation led to the realization that just calibrating the printer is not enough--that the problem additionally follows from the printer not being able to produce a good Grey scale. Whether the problem results from the operator being not quality conscious enough, or whether it arises from the lack of realization since the operator isn't called upon to print Black-White pictures, analysis revealed a need to allow for controlling the color Grey scale, as well as the characteristics of the CMYK colors themselves.